JPH09123629A - Solder paste printing and manufacture of coated plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the incidence of a fault such as electric shortcircuit caused by the crosslinking of a solder between adjacent lead wires by applying a method for printing a solder paste to a semiconductor with lead wires spaced at a pitch of 0.5mm. SOLUTION: A silicone resin liquid is poured into a metal mask 1 for printing a solder paste 5 to prepare a thermally cured coated plate. In addition, a mutually less adhesive film to the metal mask 1 and the solder paste 5 is formed on the upper surface of a protrusion on a coated plate. Further, a mutually less viscous film 4 is formed on the lateral wall of an opening part in the metal mask 1 consisting of the metal mask 1 stacked on the coated plate. Finally, the solder paste 5 is printed by transfer on the electrode terminal of a printed circuit board 7 through the metal mask 1 with a specified opening part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder paste printing method for soldering and connecting electronic components by a surface mounting method.

[0002]

2. Description of the Related Art Among surface mount type electronic parts, in order to solder a QFP or SOP type semiconductor IC package defined by the Japan Electronic Machinery Manufacturers Association to a printed wiring board, it is necessary to solder to a predetermined position shape of the printed wiring board. After the paste is printed, the semiconductor IC package is mounted so as to ride on the printed solder paste, and then the solder paste is melted and reflowed by heating. When soldering a small, multi-lead semiconductor package, the lead pitch is narrow, and the corresponding solder paste shape is also small and the pitch is narrow, resulting in imperfect solder paste print transfer. There is a tendency that the ratio of insufficient electrical connection to cause electrical connection failure or electrical short circuit due to contact of solder paste between adjacent leads is higher than that of a large-sized and small-lead semiconductor IC package.

[0003]

When a small, multi-lead semiconductor package is soldered, the lead pitch is narrowed and the corresponding solder paste shape is also small and the pitch is narrowed. The transfer is incomplete, the amount of solder paste becomes insufficient, and electrical connection failure occurs, or the solder paste contacts between adjacent leads, causing an electrical short circuit.

[0004]

In order to solve the incompleteness of solder paste printing transfer according to the prior art, a film made of a material having low mutual adhesiveness with the solder paste is formed on the side wall of the opening of the metal mask for printing the solder paste. After forming, solder paste is printed.

When a solder paste is printed after forming a film made of a material having low mutual adhesiveness with the solder paste on the side wall of the opening of the solder paste printing metal mask, the solder paste is pressed by a printing squeegee blade. Then, the space formed by the side wall of the opening of the solder paste printing metal mask and the printed wiring board on the printed surface is filled. After that, the solder paste filled in the space has a higher mutual adhesiveness between the solder paste and the printed wiring board printing surface than the opening side wall, so that it adheres to the printed wiring board printing surface. Then, it is printed and transferred.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in order of steps with reference to Examples. 1 is a cross-sectional view of an essential part showing solder printing by the method of the present invention, FIG. 2 is a cross-sectional view of an essential part corresponding to FIG. 1, showing a solder paste printed on a printed wiring board according to FIG. 1, and FIG. 1 is a sectional view of an essential part corresponding to FIG. 1 showing a process for producing a film coated plate of the present invention, and FIG. 4 is a sectional view of an essential part corresponding to FIG. 1 showing a film coated plate of the present invention.

A metal mask 1 formed by processing the stainless steel plate shown in FIG. 3 has a shape that is spread by 20 mm or more outside the outer shape of an aluminum outer frame (not shown) of the metal mask 1 and has sufficient structural strength to prevent large warpage. An aluminum plate 2 having a thickness of 3 to 5 mm is prepared, and the inside 1 of the outer edge of the aluminum plate 2 is prepared.
An aluminum square rod having a height of 10 mm and a width of 10 mm is fixed at a position of 0 mm with an epoxy resin adhesive to provide an aluminum edge (not shown), and a plate made of an aluminum material is produced.

At the time of solder paste printing of the metal mask 1 in a state where the thermosetting silicone resin liquid 3 having a viscosity of 2 to 4 Pa · s is poured into the plate at a depth of 5 to 7 mm and then sufficiently defoamed. The contact surface 1a with the surface to be printed is dipped so that the surface 1a and the aluminum plate 2 are parallel to each other and the distance is 3
Hold the silicone resin solution 3 through a holder (not shown) so that the size of the silicone resin solution 3 becomes about 4 mm, and in this state, place the silicone resin solution 3 in a large-sized constant temperature bath at a curing temperature of 100 ° C. of the silicone resin solution 3. The silicone resin liquid 3 is cured by holding it for 30 to 60 minutes which is the required curing time.

After being taken out from the large-sized constant temperature bath and cooled to room temperature, the silicone resin liquid 3a which was extruded and hardened on the surface 1b opposite to the surface 1a of the metal mask 1 and the metal blade was surfaced on the surface 1b.
The film having the protrusions 3 corresponding to the openings of the metal mask 1 in FIG. 4 is removed by cutting and removing the metal mask 1 by moving along the surface 1b while contacting the metal mask 1. A coated plate is prepared.

Next, a coating plate having silicone oil applied to the protrusions 3b is placed on and in contact with the metal mask 1, and the side wall 1c of the opening of the metal mask 1 is contacted as shown in FIG.
After forming the low-adhesion film 4 on the surface of the metal mask 1
By supplying the solder paste 5 on the surface b and moving the squeegee 6 along the surface 1 to press the solder paste 5,
After filling the space formed by the opening side wall 1c and the surface of the electrode pad 8 of the printed wiring board 7 which is the surface to be printed with the solder paste 5, when the solder mask 1 is separated from the printed wiring board 7, low adhesion is obtained. The solder paste 5 adheres to the electrode pads 8 whose adhesiveness is not lowered than to the opening side wall 1c whose adhesiveness is reduced by the film 4, and good printing can be performed.

[0011]

The solder paste printing method of the present invention is
When applied to a semiconductor package having a lead of 0.5 mm pitch, electrical connection failure due to insufficient solder amount is reduced by 70% as compared with the conventional method, and electrical short circuit failure due to solder bridging between adjacent leads is reduced. The reduction of man-hours for soldering correction is great.

[Brief description of the drawings]

FIG. 1 is a sectional view of an essential part showing solder printing by the method of the present invention.

FIG. 2 is a sectional view of a main part corresponding to FIG. 1, showing a solder paste printed on a printed wiring board according to FIG.

FIG. 3 is a diagram showing a process for producing a film-coated plate of the present invention.
Sectional drawing of the principal part corresponding to.

FIG. 4 is a cross-sectional view of a main part corresponding to FIG. 1, showing a film coating plate of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal mask, 4 ... Low adhesive film, 5 ... Solder paste, 6 ... Squeegee, 7 ... Printed wiring board, 8 ... Printed wiring board electrode terminal pad, 10 ... Solder resist.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H05K 3/34 505 7128-4E H05K 3/34 505B (72) Inventor Yoshiro Kadota 882 Ichige, Ichika, Hitachinaka City, Ibaraki Prefecture Address Company Hitachi Ltd., Measuring Instruments Division (72) Inventor Kenichi Fuchibuchi Hitachinaka City, Ibaraki Prefecture, Oji City 882 Address Corporation Hitachi Ltd. Measuring Instruments Division, (72) Inventor Hirosaki Isomae, Hitachinaka City, Ibaraki Prefecture 882 Moe Co., Ltd., Hitachi Ltd., Measuring Instruments Division (72) Inventor, Fukamizu Moroi, Hitachinaka City, Ibaraki Prefecture, Oji City 882 Mochi Co., Ltd., Hitachi Ltd., Measuring Instruments Division, (72) Inventor, Takashi Minato Tsuda, Hitachinaka City, Ibaraki Prefecture Sekiba 1939 Naka Kyoei Sangyo Co., Ltd. (72) Masao Tomioka Masao Tomioka, Hitachinaka City, Ibaraki Prefecture Tsuda Sekiba 1939 Naka Kyoei Sangyo Co., Ltd.

Claims (4)

[Claims] 1. A solder paste printing method using a metal mask having an opening of a predetermined shape at a predetermined position of a thin metal plate attached and fixed to a metal frame, wherein a silicone resin, vegetable oil, A solder paste printing method, which comprises forming a film of a material having low mutual adhesiveness with a solder paste such as animal oil. 2. The coating film of a material having low mutual adhesiveness with the solder paste according to claim 1, is formed on a projection portion of a surface of a coating film coating plate provided with a projection having a shape corresponding to the opening shape of the metal mask. It is formed by applying a film of a material having low mutual adhesiveness with a solder paste such as silicone resin, vegetable oil, animal oil, etc. in advance, and transferring it to the side wall of the opening of the metal mask by superposing it on the metal mask. Solder paste printing method. 3. The coating film-applying plate according to claim 2 is provided with an outer peripheral edge having an inner dimension having a dimension of approximately 5 mm or more outside the outer shape of the metal mask, and between the silicone resin and the outer periphery. A heat-curable silicone having a viscosity of 10 Pa · s or less and sufficient fluidity in a dish made of a material such as aluminum having a desired adhesive strength and a predetermined structure retention property before curing. After supplying the resin liquid to a predetermined depth, immerse the metal mask in the resin liquid with the contact surface of the printed surface during solder printing facing downward and maintain that state. As it is, the silicone resin liquid is treated under a predetermined heating and curing temperature condition and a time condition to cure the silicone resin liquid, and then through the opening of the metal mask, the contact surface of the printed surface during solder printing is Opposite side The protruding and cured silicone resin liquid is cut and removed by running along the metal mask surface while the metal blade is in contact with the metal mask surface so that the cured silicone resin liquid in the opening remains, and the metal mask is removed. A method for producing a film-coated plate, which is formed by peeling from a silicone resin liquid cured product. 4. A solder paste printing method, wherein a soft material such as silicone resin or polyurethane resin is used as the material of the film coating plate according to claim 3, and the film coating plate which does not damage the metal mask is used.